Radiation Dose Reduction in Digital Plain Radiography of the Knee after Total Knee Arthroplasty

Abstract

Purpose: To reduce radiation exposure of frequently performed radiographs of the knee in follow-up of total-knee arthroplasty ensuring accurate assessment by using objective quality control criteria.

Materials and Methods: In this prospective randomized study 278 radiographs of the knee in follow-up of total-knee arthroplasty were performed with standard and 37 % reduced radiation dose. The evaluation of the plain-radiographs was conducted using the following criteria: bone-implant interface, implant-surface character, implant-implant discrimination and periarticular heterotopic ossification. Two radiologists evaluated these criteria using a score ranging from 1 (definitely assessable) to 4 (not assessable). If a single criterion had been evaluated with a score ≥ 3 or more than 2 criteria with ≥ 2 points, the radiograph was score das „not assessable“. The study was designed as non-inferiority-trial.

Results: 100 % of examined radiographs were scored as assessable, hence no statistical inferiority between the examinations with standard and reduced dose could be observed. Singular assessment of the defined criteria was likewise dose-independent.

Conclusion: Plain-radiography of the knee following total-knee arthroplasty can be performed with 63 % of standard dose without loss of diagnostic validity.

Key points:

• Due to the non-inferiority of digital radiographs of the knee joint after total-knee arthroplasty done with 37 % reduced image receiver dose we recommend the tested speed class of SC 800 as a new reference value for digital radiographs with this indication.

Citation Format:

• Kloth JK, Tanner M, Stiller W et al. Radiation Dose Reduction in Digital Plain Radiography of the Knee after Total Knee Arthroplasty. Fortschr Röntgenstr 2015; 187: 685 – 690

Zusammenfassung

Ziel: Reduktion der Strahlenexposition bei häufig zu wiederholenden Projektionsradiografien des Kniegelenkes nach endoprothetischer Versorgung unter Einhaltung objektiver indikationsspezifischer Qualitätskriterien.

Material und Methoden: Prospektiv randomisiert wurden insgesamt 278 Projektionsradiografien des Kniegelenkes nach Prothesenimplantation mit Standarddosis und 37 % reduzierter Dosis durchgeführt. Die Beurteilung der Aufnahmen erfolgte anhand folgender Kriterien: Metall-Zement-Knochen-Interface, Oberflächenbeschaffenheit, Diskriminierung der Implantatkomponenten und periartikuläre Ossifikationen. Diese wurden von 2 Radiologen mit einem Score von 1 (vollständig beurteilbar) bis 4 (nicht beurteilbar) bewertet. Die Einschätzung „nicht beurteilbar“ wurde bei Bewertung eines Einzelkriteriums ≥ 3 oder zweier Kriterien ≥ 2 vergeben. Die statistische Auswertung erfolgt als Nichtunterlegenheitsanalyse.

Ergebnisse: 100 % der in die Studie eingeschlossenen Röntgenaufnahmen waren nach o. g. Score beurteilbar, somit konnte die Nichtunterlegenheit der Aufnahmen mit reduzierter Dosis bestätigt werden. Die Bewertung der Einzelkriterien war ebenfalls dosisunabhängig.

Schlussfolgerung: Röntgenuntersuchungen nach Knietotalendoprothese können ohne Verlust der diagnostischen Aussagekraft mit 63 % der Standarddosis durchgeführt werden.

Key words

skeletal-appendicular - digital radiography - radiation safety

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